The present invention relates generally to a device and minimally invasive procedure for treating a localized abnormal dilation of a lumen and more particularly, the present invention relates to a low profile stent suitable for use as a synthetic graft for the non-surgical treatment of an aneurysm, fistula, legion or the like in certain blood vessels and internal organs. The device made in accordance with the invention is retrievable and includes markers spaced about the ends of the device allowing an enhanced determination of the orientation of the device. The device is particularly well suited for delivery through a catheter or the like to a remote location in the patient""s intravenous system or in analogous vessel or organ within the patient""s body.
A wide variety of stents and grafts have been used in various medical procedures.
For example, stents and grafts (both biological and synthetic grafts) have been used to treat aneurysms and fistulas. Typically, the stent has a right circular cylindrical shape and is deliverable through a catheter to a specific location within a patient. The catheter may be used to reach a selected vessel within the vascular system wherein stenting of the vessel is desired. In U.S. Pat. No. 5,824,055 issued to Spiridigliozzi et al. a stent graft delivery system is described, wherein the graft is preferably constructed of a polyester fabric and may be held in position with a wide range of conventional stent designs. Although Spiridigliozzi et al. recognizes the need for a retrievable graft, they only describe a device that is retrievable and withdrawn when partially deployed. Hence, there is a need for a graft that is retrievable even after full deployment.
When a graft is delivered, it is also desirable to monitor the position of the graft after full deployment. Although markers capable of fluoroscopic detection have been attached to stents, the orientation of the ends of these stents remains difficult to determine when viewing the device in two dimensions. Lombardi et al. in U.S. Pat. No. 5,824,042 describes an endoluminal prostheses having position indicating markers on the prostheses, however, use of the markers to determine a rotational orientation of the ends is not described. Thus, there is a need for a stent having markers that indicate the rotational orientation of the stent, whether or not the device is viewed in two or three dimensions. The present invention addresses these and other needs that will become apparent to those skilled in the art from a review of the description of the present invention.
It is thus an object of the present invention to provide a retrievable, low-profile, self-expanding stent. The device of the present invention is preferably formed from a continuous tubular fabric, has a relaxed low-profile configuration, and includes clamps that allow for attachment of the device to an end of a delivery device or guide wire (allowing recovery of the device after deployment). In the preferred embodiment, the device is constructed from a metal fabric having a plurality of woven metal strands. The device has a proximal end and a distal end, and clamps or means for securing the metal fabric attached to each end. The clamps inhibit unraveling of the metal fabric. The configuration of the preferred embodiment has a substantially cylindrical relaxed configuration including a passageway between the two ends. Without any limitation intended, the specific shape of the device of the present invention is particularly well suited for treating an aneurysm of a vessel.
In one embodiment of the present invention, the device is constructed of a plurality of woven strands. The device has a proximal end and a distal end, each end having attached thereto a securing member that secures the woven strands together at each end, thereby inhibiting unraveling of the fabric. The device has a relaxed generally cylindrical configuration, wherein the relaxed cylindrical configuration includes a passageway extending through a central portion between each end of the device. The end portions of the device extend at an angle from the cylindrical main body portion of the device, wherein a plane of at least one end intersects a longitudinal axis of the cylindrical portion at an angle of at least one of acute and obtuse. The device further has a collapsed configuration for delivery through a catheter and channel in a patient""s body.
Additionally, at least one end of the device includes markers spaced a predetermined distance around an outer perimeter edge of the end. Also, the securing member is attachable to a delivery device. The pitch and pick of the woven strands are such that the wire mesh is inherently thrombogenic, wherein a layer of fibrin forms on the surface of the device.
In another embodiment of the present invention, the ends of the device are flared, wherein a width of the ends is greater than a midsection of the device. In yet another embodiment of the invention, an aperture is formed in the midsection of the device, and is adapted for receiving an end of another device of the present invention. In still another embodiment of the present invention, the cylindrical main body is bent and includes an aperture formed in cylindrical main body proximate the bend. A first graft of this embodiment may be stretched and partially pulled through the aperture of a second graft of this embodiment. When the first graft is allowed to resume its relaxed configuration, the first and second grafts together form a xe2x80x9cYxe2x80x9d shaped graft.
When forming these intravascular devices from a resilient fabric a plurality of resilient strands or wires are provided, with the fabric being formed by braiding the resilient strands to create a resilient material. The strands or wires have memory properties and are preferably made of a biocompatible metal alloy of known suitable construction. Either all or a portion of one or both of the outer and inner perimeter of the graft may be enclosed by a biocompatible material. Without any limitation intended, the biocompatible material may comprise a suitable known fabric manufactured by Gore, Inc. of Delaware.
In the preferred embodiment the braided fabric is deformed to generally conform to a molding surface of a molding element and the braided fabric is heat treated in contact with the surface of the molding element at an elevated temperature. The time and temperature of the heat treatment is selected to substantially set the braided fabric in its deformed state. After the heat treatment, the fabric is removed from contact with the molding element and will substantially retain its shape in the deformed state. The braided fabric so treated defines a relaxed state of a medical device which can be stretched or expanded and deployed through a catheter into a channel in a patient""s body. Those skilled in the art will appreciate that the cavities of the molds must mirror the desired shape of the device. Additionally, the mold includes cores and/or cams to adequately form the desired openings in each end of the device.
In use, a guide catheter is positioned and advanced in a patient""s body such that the distal end of the catheter is adjacent a desired treatment site for treating a physiological condition. The medical device of the present invention having a predetermined shape is then stretched and inserted into the lumen of the catheter. The device is urged through the catheter and out the distal end, whereupon, due to its ability to retain a preset configuration, it will tend to substantially return to its relaxed state adjacent the treatment site. Once the device is fully deployed, the physician or user may confirm proper deployment through radiographs, fluoroscopy, or other known non-intrusive means of observing the position of the device within the patient. The guide wire or delivery catheter is then released from the clamp and removed.